3.1.5.2 Plate Tectonics 3

Question 1

Where do young fold mountains form

Answer 1

Destructive collision zones

Question 2

Describe how young fold mountains form

E.g

Answer 2

When continental crusts meet there isn’t much subduction so their edges + sediments between them are forced up into fold mountains

Question 3

Where do rift valleys form

Answer 3

Constructive margins

Question 4

Describe how rift valleys form

E.g

Answer 4

As plates move apart in continental areas, the lithosphere stretches cussing it to fracture into parallel faults
Then the land between these faults collapses into deep, wide valleys separated by upright blocks of land called horses

E.g The Great African Rift Valley

Question 5

Where do mid-ocean ridges form

Answer 5

Constructive margins

Question 6

What are mid-ocean ridges

Answer 6

Longest,continuous uplifted structures on planet

Question 7

Describe how mid-oceanic ridges form

Answer 7

• Form when plates move apart in oceanic areas
• transform faults (regular breaks) cut across them at right angles to the plate boundary separating the ridge
• transform faults may widen at different rates causing frictional stresses forming shallow-focus earthquakes

Question 8

What is the middle of a mid-ocean ridge marked by

Answer 8

Deep rift valleys

Question 9

What can volcanic eruptions along mid-ocean ridges form

Answer 9

Submarine volcanoes that may grow to form volcanic islands over time

Question 10

Describe how deep sea trenches form

E.g

Answer 10

Where oceanic + continental crust meets, the denser oceanic plate is forced underneath (subduction)
The downwarping of the ocean plate forms a trench that’s a very deep part of the ocean

E.g Peru-chile trench -> Nazca plate subducted under South American plate

Question 11

Describe how island arcs form

Answer 11

During subduction, the descending plate encounters hotter surroundings which melts the plate
As this material is less dense than surroundings, it begins to rise towards surface as magma
When this reaches surface it forms composite + explosive volcanoes

If eruptions take place off shore, volcanic islands form (island arcs)

Question 12

What causes hot spots to form around the earth’s core

What do these hot spots do

Answer 12

Radioactive decay in the core

They heat the lower mantle creating localised thermal currents where magma plumes rises vertically

Question 13

What volcanoes form from magma plumes (basaltic lava)

Answer 13

Large, flat shield volcanoes

Question 14

What is created as the plate moves over the magma plume

E.g

Answer 14

A chain of extinct + active volcanoes form - archipelago

E.g the Hawaiian Archipelago

Question 15

What was the first island (submarine volcano) that the Pacific Oceans hot spot created 4.6 million years ago

Answer 15

Island of Kauai